Editing Lens (section)

==== Sign convention for other parameters ====
{| class="wikitable sortable mw-collapsible"
|+ Sign convention for Gaussian lens equation<ref name="Hecht-2017a" />
! Parameter
! Meaning
! + Sign
! − Sign
|-
|align=center| {{mvar|s}}<sub>o</sub>
| The distance between an object and a lens.
| Real object
| Virtual object
|-
|align=center| {{mvar|s}}{{sub|i}}
| The distance between an image and a lens.
| Real image
| Virtual image
|-
|align=center| {{mvar|f}}
| The focal length of a lens.
| Converging lens
| Diverging lens
|-
|align=center| {{mvar|y}}{{sub|o}}
| The height of an object from the optical axis.
| Erect object
| Inverted object
|-
|align=center| {{mvar|y}}{{sub|i}}
| The height of an image from the optical axis
| Erect image
| Inverted image
|-
|align=center| {{mvar|M}}{{sub|T}}
| The transverse magnification in imaging (&nbsp;{{math|{{=}}}} the ratio of {{mvar|y}}{{sub|i}} to {{mvar|y}}{{sub|o}}&nbsp;).
| Erect image
| Inverted image
|}
This convention is used in this article. Other conventions such as the [http://hyperphysics.phy-astr.gsu.edu/hbase/geoopt/lenseq.html#c2 Cartesian sign convention] change the form of the equations.